Change default DNS on openvpn connect

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http://unix.stackexchange.com – I am using Network Manager on Ubuntu 12.10 to connect to an openvpn server. The connection works without problems. However, when I connect, I would like to change my default DNS server to a server on the vpn network. That way I can use domain names that are only defined on the vpn network. Is there a way I can make this automatic with Network Manager? I can also change settings on the openvpn server if that is the way I need to go. Thanks! (HowTos)